Is this delamination or something else?

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James

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I was polishing the spine of a new gyuto when I noticed this very thin yet palpable crack. The knife is a clad carbon knife so delamination might be the culprit. I would like some second opinions (hopefully telling me it's nothing) before I talk to the vendor. So what are your opinions?

bNmPdIH.jpg

a0BwR7C.jpg
 
James said:
I was polishing the spine of a new gyuto when I noticed this very thin yet palpable crack. The knife is a clad carbon knife so delamination might be the culprit. I would like some second opinions (hopefully telling me it's nothing) before I talk to the vendor. So what are your opinions?

bNmPdIH.jpg

a0BwR7C.jpg
Click to expand...

What kind of knife is it? Can't tell from the pics, but could be delamination. We're you sanding down the spine?
 
It's a Kato. I did sand down the spine with 1500 grit wet/dry (didn't go lower than this) for about 2 minutes before I noticed it. I'll try to get some better pictures. What angles would be more diagnostic?
 
some kind of acid etch would bring out the contrast between core and cladding... then you can see if this follows along that connection point. If it does, then it may be delamination. If not, maybe a crack in the steel. Also, it may not be a big problem at all... for example, it could be rather shallow, and might come out with a tiny bit of work. Or, on the flip side, it could get bigger with time. For example, i was just sharpening a damascus yanagiba and i noticed that there was some delamination in the damascus cladding inbetween layers. It started off small and got bigger as i sharpened. It might go away, but in this case, it looks pretty deep, so i'm not sure how quickly it will disappear.
 
Thanks for all of the advice Jon. I emailed Maxim and the knife and ran the acid etching by him. Will update this thread when things get moving.
 
yeah... for what its worth, i'm not a huge fan of acid etching things (aesthetically), but it does make for an easy way to see differences in steel layers. It could be as simple as making a paste of BKF, rubbing a bit on the spine, and letting it sit for a bit.

Also, for what its worth, although no one wants to see delamination, it can be a good sign with regard to good low temp forging. As one who has made knives before, and one who also happens to sell them, we always do our best to weed out things like this, but sometimes they are not visible at first (or for a very long time), and most times, they self correct quickly (after slight steel removal), so please try to be understanding (not necessarily directed towards you James, but for others reading this thread... people tend to get uptight about stuff like this)
 
Just curious, what does it mean with regards to low temp forging? With regard to quality control, I definitely understand. I had given the knife a very thorough look after receiving it, but didn't notice this. The delamination/crack/whatever is about the width of a hair at its widest point and only palpable with a fingernail. Doing this to hundreds of knives is absolutely mindblowing and customers appreciate it.

Also, would it be possible to seal it with some resin, CA glue or lacquer to prevent encountering problems in the future?
 
james... maybe possible with ca glue or something similar... never tried though.

With regard to low temp forging, it has a lot to do with grain size/growth. However, low temps also make forgewelding a bit more difficult. Most blacksmiths in japan that i've trained under do their best to forge at as low of a temp as they can.... however, lower temps mean that finding delmaination is a bit more common. In a lot of ways, it can be a good sign that the blacksmith is trying to control grain size properly. However, if you see a lot of delamination rather often, that is not a good sign. Also, the most severe ones are usually caught before shipping out in my experience.
 
It seems like for some case, we can't see the problem not until we sharpen or polish, etc, the knife?
And will this happen to non-damascus, more often?
 
this can happen on any clad knife... damascus or not. It is more likely to happen on hand forged knives, forged at lower temps. Much less likely in knives made from pre-clad sheets for example (as the sheets are often down with higher temps and more advanced equipment.

Carter actually does a great job explaining the concepts in this video:
[video=youtube;28UyWZ-mLpw]https://www.youtube.com/watch?v=28UyWZ-mLpw[/video]
 
Thanks Jon Explaining all for me here :)
James I send you email
 
Murray looks way cooler with a mustache! Kinda got a Chuck Norris meets Magnum P.I. thing going on.
 
Thanks Maxim! Like you said in the email, just a line in the steel. I spent a few minutes on it with 300 grit sandpaper and it disappeared.

Once again, thanks for the responses Jon. They were very enlightening.
 
By the way, how can you tell it is delamination or a void?
 
Actually I should say nick and delamination. I notice something like a knife made from tamahagane has nicks. How can I tell it is not delamination.
 
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